Yingchang Jiang

Effect of temperature, chloride ion and pH on the crevice corrosion behavior of SAF 2205 duplex stainless steel in chloride solutions

An investigation was conducted to examine the crevice corrosion behaviors for SAF 2205 duplex stainless steel in NaCl solutions by using potentiostatic critical crevice temperature measurement. Potentiodynamic polarization technique was comparably used to study the electrochemical behavior. The influence of temperature, chloride concentration and pH on the critical crevice temperature and electrochemical behavior in NaCl solutions was studied. The critical crevice temperature of SAF 2205 DSS in 4% NaCl solution was about 28xa0°C. The critical crevice temperature decreased linearly with an increase in log [Cl−]. A maximum critical crevice temperature was found in 4% NaCl solutions at pH 8.5. The influence of the duplex microstructure on attack development and morphology was analyzed by scanning electron microscope.

In-situ Growth of Layered Bimetallic ZnCo Hydroxide Nanosheets for High-Performance All-Solid-State Pseudocapacitor

Two-dimensional (2D) hydroxide nanosheets can exhibit exceptional electrochemical performance owing to their shortened ion diffusion distances, abundant active sites, and various valence states. Herein, we report ZnCo1.5(OH)4.5Cl0.5·0.45H2O nanosheets (thickness ∼30 nm) which crystallize in a layered structure and exhibit a high specific capacitance of 3946.5 F g-1 at 3 A g-1 for an electrochemical pseudocapacitor. ZnCo1.5(OH)4.5Cl0.5·0.45H2O was synthesized by a homogeneous precipitation method and spontaneously crystallized into 2D nanosheets in well-defined hexagonal morphology with crystal structure revealed by synchrotron X-ray powder diffraction data analysis. In situ growth of ZnCo1.5(OH)4.5Cl0.5·0.45H2O nanosheet arrays on conductive Ni foam substrate was successfully realized. Asymmetric supercapacitors based on ZnCo1.5(OH)4.5Cl0.5·0.45H2O nanosheets @Ni foam// PVA, KOH//reduced graphene oxide exhibits a high energy density of 114.8 Wh kg-1 at an average power density of 643.8 W kg-1, which surpasses most of the reported all-solid-state supercapacitors based on carbonaceous materials, transition metal oxides/hydroxides, and MXenes. Furthermore, a supercapacitor constructed from ZnCo1.5(OH)4.5Cl0.5·0.45H2O nanosheets@PET substrate shows excellent flexibility and mechanical stability. This study provides layered bimetallic hydroxide nanosheets as promising electroactive materials for flexible, solid-state energy storage devices, presenting the best reported performance to date.

Charge Transfer in Ultrafine LDH Nanosheets/Graphene Interface with Superior Capacitive Energy Storage Performance

Two-dimensional LDH nanosheets recently have generated considerable interest in various promising applications because of their intriguing properties. Herein, we report a facile in situ nucleation strategy toward in situ decorating monodispersed Ni-Fe LDH ultrafine nanosheets (UNs) on graphene oxide template based on the precise control and manipulation of LDH UNs anchored, nucleated, grown, and crystallized. Anion-exchange behavior was observed in this Ni-Fe LDH UNs@rGO composite. The Ni-Fe LDH UNs@rGO electrodes displayed a significantly enhanced specific capacitance (2715F g-1 at 3 A g-1) and energy density (82.3 Wh kg-1 at 661 W kg-1), which exceeds the energy densities of most previously reported nickel iron oxide/hydroxides. Moreover, the asymmetric supercapacitor, with the Ni-Fe LDH UNs @rGO composite as the positive electrode material and reduced graphene oxide (rGO) as the negative electrode material, exhibited a high energy density (120 Wh kg -1) at an average power density of 1.3 kW kg -1. A charge transfer from LDH layer to graphene layer, which means a built in electric field directed from LDH to graphene can be established by DFT calculations, which can significantly accelerate reaction kinetics and effectively optimize the capacitive energy storage performance.

Rapid Amorphization in Metastable CoSeO3·H2O Nanosheets for Ultrafast Lithiation Kinetics

The realization of high-performance anode materials with high capacity at fast lithiation kinetics and excellent cycle stability remains a significant but critical challenge for high-power applications such as electric vehicles. Two-dimensional nanostructures have attracted considerable research interest in electrochemical energy storage devices owing to their intriguing surface effect and significantly decreased ion-diffusion pathway. Here we describe rationally designed metastable CoSeO3·H2O nanosheets synthesized by a facile hydrothermal method for use as a Li ion battery anode. This crystalline nanosheet can be steadily converted into amorphous phase at the beginning of the first Li+ discharge cycling, leading to ultrahigh reversible capacities of 1100 and 515 mAh g-1 after 1000 cycles at a high rate of 3 and 10 A g-1, respectively. The as-obtained amorphous structure experiences an isotropic stress, which can significantly reduce the risk of fracture during electrochemical cycling. Our study offers a precious opportunity to reveal the ultrafast lithiation kinetics associated with the rapid amorphization mechanism in layered cobalt selenide nanosheets.

In situ growth of (NH4)2V10O25·8H2O urchin-like hierarchical arrays as superior electrodes for all-solid-state supercapacitors

Hierarchical nanostructures with highly exposed active surfaces for use in high-performance pseudocapacitors have attracted considerable attention. Herein, we developed a one-step method for the in situ growth of (NH4)2V10O25·8H2O urchin-like hierarchical structures on highly conductive nickel foam substrates for use as advanced electrodes for all-solid-state asymmetric supercapacitors. The in situ growth of (NH4)2V10O25·8H2O urchin-like hierarchical structures delivers a specific capacitance of 1530 F g−1 at a current density of 1.5 A g−1, and retains 95.1% of the initial capacitance after 10u2006000 cycles, owing to the advantages of the urchin-like hierarchical structure such as more active sites for electrochemical reactions, as well as a shortened diffusion length for the charge carriers due to a binder-free effect, which exceeds that of most recently reported vanadates and polyvanadates. The as-assembled all-solid-state (NH4)2V10O25·8H2O@Ni//PVA/KOH//RGO@Ni device exhibits a comparable capacity of 92.2 F g−1 at a current density of 0.4 A g−1 and excellent cycling performance through 5000 cycles. Our study provides rational guidance toward the design of novel hierarchical nanostructures of polyvanadate for solid-state supercapacitors with superior electrochemical performances in long-term cycling stability and high energy density.